Android Studio 中下载文件夹中的文件选择器出现错误

问题描述 投票：0回答：2

我的问题

我目前正在使用 Android Studio 开发 Android 应用程序。 要选择文件，用户单击按钮，资源管理器将打开，他可以选择文件。 在这个过程中，我使用了一个名为 

FileChooser.java
的辅助类。只要用户不从下载文件夹中选择文件，整个系统就可以很好地工作。

如果用户尝试从下载文件夹中选择文件，则会发生以下情况：

NumberFormatException: for input string: "msf:80123"

FileChooser 返回的 URL：

content://com.android.providers.downloads.documents/document/msf:80662

这是因为辅助类需要长类型。删除 

msf:
并将 
ID
添加到末尾也不起作用。似乎 
Android
将此 
msf:
标签添加到了下载文件夹中的所有内容。

我也在寻找一种有效的解决方案来从下载文件夹中调用文件。

召唤

Uri selectedFile = data.getData();
InputStream dataStream = new FileInputStream(FileChooser.getPath(getContext(), selectedFile));

FileChooser 类中的异常调用

 final Uri contentUri = ContentUris.withAppendedId(
       Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));

帮助类FileChooser

package com.example.dsvconverter.helper;

import android.content.ContentUris;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.provider.DocumentsContract;
import android.provider.MediaStore;


public class FileChooser {

    /**
     * Get a file path from a Uri. This will get the the path for Storage Access
     * Framework Documents, as well as the _data field for the MediaStore and
     * other file-based ContentProviders.
     *
     * @param context The context.
     * @param uri The Uri to query.
     * @author paulburke
     */
    public static String getPath(final Context context, final Uri uri) {

        final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;

        // DocumentProvider
        if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
            // ExternalStorageProvider
            if (isExternalStorageDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];

                if ("primary".equalsIgnoreCase(type)) {
                    return Environment.getExternalStorageDirectory() + "/" + split[1];
                }

                // TODO handle non-primary volumes
            }
            // DownloadsProvider
            else if (isDownloadsDocument(uri)) {

                final String id = DocumentsContract.getDocumentId(uri);
                final String[] split = id.split(":");
                final String type = split[0];

                final Uri contentUri = ContentUris.withAppendedId(
                        Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));

                return getDataColumn(context, contentUri, null, null);
            }
            // MediaProvider
            else if (isMediaDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];

                Uri contentUri = null;
                if ("image".equals(type)) {
                    contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                } else if ("video".equals(type)) {
                    contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
                } else if ("audio".equals(type)) {
                    contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
                }

                final String selection = "_id=?";
                final String[] selectionArgs = new String[] {
                        split[1]
                };

                return getDataColumn(context, contentUri, selection, selectionArgs);
            }
        }
        // MediaStore (and general)
        else if ("content".equalsIgnoreCase(uri.getScheme())) {
            return getDataColumn(context, uri, null, null);
        }
        // File
        else if ("file".equalsIgnoreCase(uri.getScheme())) {
            return uri.getPath();
        }

        return null;
    }

    /**
     * Get the value of the data column for this Uri. This is useful for
     * MediaStore Uris, and other file-based ContentProviders.
     *
     * @param context The context.
     * @param uri The Uri to query.
     * @param selection (Optional) Filter used in the query.
     * @param selectionArgs (Optional) Selection arguments used in the query.
     * @return The value of the _data column, which is typically a file path.
     */
    public static String getDataColumn(Context context, Uri uri, String selection,
                                       String[] selectionArgs) {

        Cursor cursor = null;
        final String column = "_data";
        final String[] projection = {
                column
        };

        try {
            cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs,
                    null);
            if (cursor != null && cursor.moveToFirst()) {
                final int column_index = cursor.getColumnIndexOrThrow(column);
                return cursor.getString(column_index);
            }
        } finally {
            if (cursor != null)
                cursor.close();
        }
        return null;
    }


    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is ExternalStorageProvider.
     */
    public static boolean isExternalStorageDocument(Uri uri) {
        return "com.android.externalstorage.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is DownloadsProvider.
     */
    public static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is MediaProvider.
     */
    public static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }
}

更新：
@blackapps 提供的代码有效，但是现在我遇到了新问题。

Blackapps 代码：

InputStream dataStream = getContentResolver().openInputStream(data.getData());

这个解决方案有效，但现在有些不同了。我正在制作一个PGP工具，这个

InputStream
包含从所选文件中读取的公钥。如果我按照您的方式创建 InputStream，PGP 库 不再将其识别为 
公钥
。但是，如果我将其打印到控制台，它看起来是正确且相同的。

问题：

为什么 @Blackapps 解决方案有效，但库不再将其识别为公钥，即使打印的字符串是 1:1 相同？

java android file android-studio explorer
2个回答
7
投票

唯一的问题是获取下载目录的路径或msf和NumberFormat异常，试试这个。它对我来说正确有效

package com.example.bookingmelbourne;
import android.content.ContentUris;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.provider.OpenableColumns;
import android.text.TextUtils;
import android.util.Log;

import androidx.annotation.Nullable;
import androidx.annotation.WorkerThread;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class FileUtils {
    private static final String TAG = "FileUtils";
@WorkerThread
@Nullable
public static String getReadablePathFromUri(Context context, Uri uri) {

    String path = null;
    if ("file".equalsIgnoreCase(uri.getScheme())) {
        path = uri.getPath();
    }

    if (Build.VERSION.SDK_INT > Build.VERSION_CODES.KITKAT) {
        path = getPath(context, uri);
    }

    if (TextUtils.isEmpty(path)) {
        return path;
    }

    Log.d(TAG, "get path from uri: " + path);
    if (!isReadablePath(path)) {
        int index = path.lastIndexOf("/");
        String name = path.substring(index + 1);
        String dstPath = context.getCacheDir().getAbsolutePath() + File.separator + name;
        if (copyFile(context, uri, dstPath)) {
            path = dstPath;
            Log.d(TAG, "copy file success: " + path);
        } else {
            Log.d(TAG, "copy file fail!");
        } 
    }
    return path;
}

public static String getPath(final Context context, final Uri uri) {
    final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
    if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
        if (isExternalStorageDocument(uri)) {
            final String docId = DocumentsContract.getDocumentId(uri);
            Log.d("External Storage", docId);
            final String[] split = docId.split(":");
            final String type = split[0];

            if ("primary".equalsIgnoreCase(type)) {
                return Environment.getExternalStorageDirectory() + "/" + split[1];
            }
        } else if (isDownloadsDocument(uri)) {

            String dstPath = context.getCacheDir().getAbsolutePath() + File.separator + getFileName(context,uri);

             if (copyFile(context, uri, dstPath)) {
                Log.d(TAG, "copy file success: " + dstPath);
                return dstPath;

            } else {
                Log.d(TAG, "copy file fail!");
            }


        } else if (isMediaDocument(uri)) {
            final String docId = DocumentsContract.getDocumentId(uri);
            final String[] split = docId.split(":");
            final String type = split[0];

            Uri contentUri = null;
            if ("image".equals(type)) {
                contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
            } else if ("video".equals(type)) {
                contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
            } else if ("audio".equals(type)) {
                contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
            }

            final String selection = "_id=?";
            final String[] selectionArgs = new String[]{split[1]};
            return getDataColumn(context, contentUri, selection, selectionArgs);
        }
    } else if ("content".equalsIgnoreCase(uri.getScheme())) {
        return getDataColumn(context, uri, null, null);
    } else if ("file".equalsIgnoreCase(uri.getScheme())) {
        return uri.getPath();
    }
    return null;
}

public static String getFileName(Context context, Uri uri) {

    Cursor cursor = context.getContentResolver().query(uri,null,null,null,null);
    int nameindex = cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME);
    cursor.moveToFirst();

    return  cursor.getString(nameindex);
}


private static String getDataColumn(Context context, Uri uri, String selection,
                                    String[] selectionArgs) {
    Cursor cursor = null;
    final String column = "_data";
    final String[] projection = {column};

    try {
        cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs,
                null);
        if (cursor != null && cursor.moveToFirst()) {
            final int column_index = cursor.getColumnIndexOrThrow(column);
            return cursor.getString(column_index);
        }
    } finally {
        if (cursor != null)
            cursor.close();
    }
    return null;
}

private static boolean isExternalStorageDocument(Uri uri) {
    return "com.android.externalstorage.documents".equals(uri.getAuthority());
}

private static boolean isDownloadsDocument(Uri uri) {
    return "com.android.providers.downloads.documents".equals(uri.getAuthority());
}

private static boolean isMediaDocument(Uri uri) {
    return "com.android.providers.media.documents".equals(uri.getAuthority());
}

private static boolean isReadablePath(@Nullable String path) {
    if (TextUtils.isEmpty(path)) {
        return false;
    }
    boolean isLocalPath;
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
        if (!TextUtils.isEmpty(path)) {
            File localFile = new File(path);
            isLocalPath = localFile.exists() && localFile.canRead();
        } else {
            isLocalPath = false;
        }
    } else {
        isLocalPath = path.startsWith(File.separator);
    }
    return isLocalPath;
}

private static boolean copyFile(Context context, Uri uri, String dstPath) {
    InputStream inputStream = null;
    OutputStream outputStream = null;
    try {
        inputStream = context.getContentResolver().openInputStream(uri);
        outputStream = new FileOutputStream(dstPath);

        byte[] buff = new byte[100 * 1024];
        int len;
        while ((len = inputStream.read(buff)) != -1) {
            outputStream.write(buff, 0, len);
        }
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    } finally {
        if (inputStream != null) {
            try {
                inputStream.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        if (outputStream != null) {
            try {
                outputStream.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    return true;
}

  }

之后，您可以调用此方法传递上下文和uri对象

 String realPath = FileUtils.getReadablePathFromUri(context,uri)
5
投票

在 onActivityResult() 中：

InputStream dataStream = getContentResolver().openInputStream(data.getData());

扔掉 getPath() 函数。

这适用于所有的人。

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